HOW IT HAPPENED:» I saved my file» Pasted something in the file and it beachballed» Tried to forcequit photoshop» Didn't close the file or any other files» Chose to hard restart comp, then I opened that file back up, and it shows a prompt stating, "could not complete your request because the file is not compatible with this version of photoshop"

You can't. Best you can do now is to limit how much of your life you are going to devote to trying to ressurrect the file, and then bemoaning and/or mourning the loss of your work, the waste of your time.

Cut immediately to the chase. End the wasted time right now by starting again from whatever artefacts you may have or from scratch if you have no artefacts.

DO IT. DO IT NOW. DON'T WAIT FOR A BETTER ANSWER, TAKE THIS ONE AND GET BACK ON IT IMMEDIATELY.

there are several freeware apps out there that read psd's. i'd open it with them to see if any can at least grab the layers so you'll have something to start over with. have you tried other apps like gimp?